Aldosterone, water, and bipedalism

This is, as I mentioned, a fascinatingly
thorny little thicket involving some persistent "false facts" begun by
Elaine Morgan in her 1990 book, The Scars of Evolution, and repeated
by others since.
At its heart is a central contention of the Aquatic
Ape Theory: a major reason that these water environments were necessary
for the evolution of bipedalism is to help support the body weight of our
ancestors while walking upright.
Hardy made quite a point of this
in his first article on the subject, and it has been a central tenet since.
Morgan devoted an entire chapter to it in The Scars of Evolution
(Chapter 3, "The Cost of Walking Erect", and part of chapter 4).
It was there she brought up the aldosterone evidence...

Wait, just a sec... I can't
keep typing without mentioning this.
Sorry, but this one just slays me.
Back when I was posting on this subject in the sci.anthropology.paleo
newsgroup, Elaine made the most amazing claim.
I have to mention
it -- it's even apropos, since it sheds light on her research and debating
style.
Here's what she said about this on the 4th of July, 1995:

"I would like to reply
to some serious misrepresentations.

"Jim Moore says that "all"
(sic) supporters of AAT claim that a major reason for the evolution of
bipedalism was that wading in water helped to support the body weight.
I do not know of anybody that says this."

Frankly, I was astonished.
I mean, she did get the theory from Hardy; she reprinted his articles on
the subject in her 1982 book.
Didn't she ever actually read
his work?
But more than that, what astonished me was that barely
5 years before she posted, she'd published an entire chapter and a half
on just that point.
Now, I've seen authors who were ignorant of writings
that contradicted their position, and I've seen authors who were ignorant
of writings that support their position, but I've never seen another writer
who was so ignorant of what they themselves had written.
Incredible.

1990 The Scars of Evolution
Elaine Morgan.
Souvenir Press: London

pg. 47:
In the aquatic scenario the
position is reversed.
Walking erect in flooded terrain was less an
option than a necessity.
The behavioural reward -- being able to
walk and breathe at the same time -- was instantly available.
And most of the disadvantages of bipedalism were cancelled out.
Erect posture imposes
no strain on the spine under conditions of head-out immersion in water.
There is no added weight on the lumbar vertebrae.
The discs are not
vertically compressed.
(An astronaut in zero gravity gains an inch
in height in space, and immersion in water is the nearest thing to zero
gravity on planet Earth.)
pp. 47-48:
Water thus seems to
be the only element in which bipedalism for the beginner may have been
at the same time compulsory and relatively free of unwelcome physical consequences.

From these quotes you can see
that the support provided by water is considered to be a critically important
part of the purported aquatic transition to bipedalism.
Despite Morgan's
claim to the contrary.

Okay, I'm better now.
Where was I?
Oh yeah...

It was there (chapters 3 and
4 of Scars) she brought up the aldosterone evidence.
Aldosterone is a hormone which regulates salt balance in the body (there's a lot of
salt-related material in the AAT/H, and therefore on this site).
Let's see what she has to say:

1990 The Scars of Evolution
Elaine Morgan.
Souvenir Press: London.

pp. 31-32:
"Endocrine glands sited above
the kidneys produce hormones which respond to actual or potential physical
'emergencies'.
The best known is adrenalin (epinephrine), the 'flight-or-fight'
hormone.
In situations arousing fear or anger it causes sugar to
be released into the bloodstream supplying instant energy, plus clotting
agents in case the situation leads to violence and bloodshed.
A hormone which
responds to 'emergencies' of a different kind is aldosterone.
Its function is to regulate blood pressure, and to inhibit the excretion of
salt.
The 'emergencies' which stimulate the production of aldosterone
are listed in medical textbooks as:
1 surgery;
2 anxiety;
3 a diet deficient in
salt;
4 haemorrhage;
5 standing up.
The first four items apply
to all mammals and are readily understandable.
If there is a deficiency
of salt in the body tissues, aldosterone conserves salt by preventing its
excretion into the urine.
Loss of blood due to surgery or haemorrhage
means that the blood volume must be restored; the action of aldosterone
increases the fluid volume of the blood.
As for acute anxiety, some
of the physical manifestations (sweating, vomiting, loosening of the bowels)
are notorious squanderers of salt reserves.
An increase in aldosterone
production will guard against all these contingencies, since this hormone
can inhibit salt excretion in the sweat and faeces as well as in urine.
The fifth 'emergency'
(standing up) applies particularly to bipeds.
Rising from bed or
from a chair produces a six-fold increase in the amount of aldosterone
in the blood.
This bears no relation to the amount of exertion needed
to attain or sustain erect posture.
Experiments have been conducted
where a volunteer is strapped to a pivoting board which can be tilted on
its axis, thus raising the body to the perpendicular with no physical effort
involved.
The production of aldosterone still rises just as steeply.
The explanation
once again lies in the pull of gravity on the bloodstream.
When we
stand up, the blood tends to drain away from the head and the heart and
pool in the lower limbs.
It so happens that the main baroceptors
which monitor changes in blood pressure are situated in the neck.
For a quadruped this is a perfectly appropriate site; blood pressure at
this point will be fairly representative of the pressure throughout the
body; when these baroceptors register a change in blood pressure, they
trigger appropriate responses such as increased output of aldosterone.
But the receptors
are incapable of distinguishing between the 20 per cent drop in pressure
which would result from a massive haemorrhage in a quadruped, and the 20
per cent drop in the head and neck region which signals in a biped the
act of standing up.
The aldosterone levels respond in the same manner
to standing up as to surgery."

Now that sounds serious.
Thankfully there's a solution at hand for those poor hominids:

pg. 47 (Ibid.):
"Standing up in water
does not trigger secretion of aldosterone, salt retention or higher blood
pressure.
The reverse is the case: head-out immersion causes a prompt
and marked fall in systolic and diastolic blood pressure,
plus increased excretion of salt in the urine."

Lucky little buggers.
If only it were true...

The reality about the standing up "emergency"

As is common with Morgan research,
it's hard to know where to start in pointing out errors; I think we'll
start with her list, as "listed in medical textbooks".
She left out
a few key points.
Before I get into particulars, maybe I should make
a point clear.
When I initially researched Morgan's statements in
these chapters, I found she was wrong about many points, but I couldn't
tell at that time whether she was wrong because she'd used references which
were wrong or whether she had accurate references but misrepresented what
they said.
As a student of the history of science, I wanted to know
which it was.
So in December 95, in sci.anthropology.paleo, I asked
her to provide those refs (she'd by that time said she was more than willing
to do so), and eventually, she posted them.
The refs were good, in
fact, I had found them already in my own research on the subject.
The list she got from the Encyclopedia Britannica, which I hadn't
used but when I checked it out, it was the exact same list I'd found in
William Ganong's 1993 Review of Medical Physiology.
There are some interesting differences between the list in these books and the
list in Morgan's book.

In her book, Morgan uses a
rhetorical device which seems to be an attempt to get the reader to think
that not just these aldosterone receptors, but the total animal
would "respond in the same manner" to standing up as it would to massive
hemorrhage or to surgery.
But of course many other factors would
enter in and create a massive difference between the two types of stimuli.
Morgan, by carefully crafting the false context that these books
consider all the items on this list to be "emergencies", fails to differentiation
between several distinct types of causes of this aldosterone build-up.
Both the textbook and encyclopedia article, however, point out that the
actual
emergencies (surgery, anxiety, physical trauma, and hemorrhage)
as opposed to normal bodily functions (like standing up, which Morgan inaccurately lumps in with the emergencies) and slow-onset illnesses, also cause
an increased excretion of powerful steroids called glucocorticoids.
They point out that these glucocorticoid levels are unaffected by
high potassium intake, low sodium intake, constriction of interior vena
cava in thorax, standing, and secondary hyperaldosteronism (in some cases of
congestive heart failure, cirrhosis, and nephrosis).

While Morgan's list mixes together
these normal life events (like standing up) and slow-onset diseases with actual emergencies
and clearly implies that the sources call them all emergencies (as she
does) the sources themselves don't do that.
It was merely Morgan's invention.

The reality of water immersion

The second part of Morgan's claim
rests on scientific experiments on the effects of water immersion therapies.
She presents the results in the section on page 47 of The Scars of Evolution:

"Standing up in water
does not trigger secretion of aldosterone, salt retention or higher blood
pressure.
The reverse is the case: head-out immersion causes a prompt
and marked
fall in systolic and diastolic blood pressure,
plus increased excretion of salt in the urine."

With these statements, Morgan
completes her argument that our hominid ancestors would be able to stand
up in water without the temporary effects of blood pressure drop and rise
in aldosterone.
Of course the effects of these changes when standing
up are actually pretty minor, as even Morgan admits ("It is a system which
works smoothly and is in general benign." Ibid. pg. 33), but perhaps a
case could be made that things might have been easier for our ancestors
without it.
Morgan tries to make that case, as seen above, and it
would make a lot of sense... if it were true.

You see, these changes during
water immersion don't happen in time to prevent these very temporary effects
of standing up, as Morgan suggests.
Her source, Murray Epstein (who
actually is an experienced researcher on this subject) points out that
the aldosterone drop during immersion Morgan is so happy to see isn't a
quick one, as it would have to be for it to be a benefit in the aquatic ape scenario; instead it begins "as early as 60 min of immersion" (Epstein 1984. pg. 181).
The increased excretion of salt Morgan mentions takes even
longer to come about, several hours after the increased excretion of urine
(which is why you can get dehydrated in water unless you can drink it;
of course in the commonly postulated AAT/H saltwater environment you can't drink it).
The increase in urine excretion itself doesn't happen for an
hour or so after immersion either.
Epstein also notes the blood pressure decrease
isn't quite so dramatic as Morgan seems to imply ("water immersion is associated
with a significant, albeit slight, decrease in mean arterial blood
pressure", Epstein et al. 1978, pg. 495 [italics in original]).

These changes do not happen quickly, as Morgan suggests and as her scenario requires.
They also don't happen unless you're in water up to your neck (or higher), which is also a problem for the wading aquatic ape.
For the changes to have a helpful effect when we stand up, these bipedal hominids
would have to always enter the water by crawling (or maybe scooting in
on their rear ends) and then stand up only after an hour or so.
Hard to see where that helps you in the common AAT/H scenario of running into
the water to escape predators.
Maybe they could scoot really fast.

Another interesting fact is that the reflex which causes all the above (the Henry-Gauer Reflex) is not present in seals.
It's highly likely that it isn't present in other aquatic mammals, but that hasn't been studied, as far as I know.
However, Morgan thinks it's evidence of an aquatic past, when the reality is that this is something we would expect to see eliminated by an aquatic past

By the way, in this section of The Scars of Evolution
Morgan also attempts to contrast the hormone situation regarding adrenalin in humans
with that seen in quadrupeds by intimating that other animals live free of stress by
either predators or each other:

1990 The Scars of Evolution
by
Elaine Morgan.
Souvenir Press: London.

pg. 33:
"A quadruped in a secure environment
may spend weeks at a time stress free and with no need for these glands
to be activated until the rutting season comes round."

Where on the actual earth would
we find these quadrupeds which live in such a "secure environment" that
they can "spend weeks at a time stress free and with no need for these
glands to be activated"? why has there never been a Nature
show or National Geographic article about this predator-free Nirvana?
what about the squabbling and fighting that goes on over food and water
in most species? has Morgan never even, say, fed ducks at a city
park?